Muffler



Feb. 28, 1939. G. A. KINGsLi-:Y

MUFFLEH Filed April 5, 1935 A mi m @j ja .qd 5, ,l H Lv. A 6 M 6 NT NQ Q MFN.. QV, QN *v hh. NVJ 4. \mh. v W

Nv\\\\\\\\\\\ \\\\\\\\\\\\\W\\\\\\\M Patented Feb. 28, 1939 UNITED STATES PATENT OFFICE MUFFLER Application April 5, 1935, Serial No. 14,849

12 Claims.

The invention relates generally to muiilers, and has particular reference to mufllers for the suppression of the noise of the discharge of exhaust gases of internal combustion engines without the creation of excessive back pressure.

In the design of muffler constructions for internal combustion engines of automotive vehicles, it is not sufficient to consider only the suppression of the noise of the exhaust gases. Frequently, in automotive vehicles at definite engine speeds, the numerous vibrations result from the operation become in tune and by a purely additional effect objectional noise periods are experienced by occupants of the vehicle compartment. It has been found that the magnitude and occurrence of these periods may be materially reduced or even eliminated through the regulation of the pitch or frequency of the muliler to place it out-of-phase with the frequency of other sources of sound wave emanation. Thus it is important that the mufller design not only be effective in sound suppression arising in the exhaust system, but it is highly desirable that it be such as to permit control of its pitch or frequency as to throw'it out of phase with other sources of sound wave emanation associated with the Vehicle.

An object of the invention is to provide a muffler of the straight through acoustic labyrinth type capable of converting the gas flow from pulsating low velocity pressure to a more even flow high velocity pressure without seriously increasing thestatic pressure of the entire system measured at the engine manifold.

An object of the invention is to provide a straight through muffler in which the frequency or tone of the muiller may be readily changed in production without seriously affecting the back pressure of the system measured at the manifold.

A further object is to provide a straight through mufller of an acoustic labyrinth type in which improved sound wave cancellation effect result.

Other objects and advantages residing in the arrangement, construction and combination of parts as will be set forth and appear from the description to follow when considered in connection with the accompanying drawing wherein Fig. 1 is a broken longitudinal cross-sectional view taken upon the vertical center line of the muffler construction, and

Fig. 2 is a cross-section taken on line II-II of Fig. 1.

When generally considered, the muffler of the present invention embodies a construction in whichV the major portion o-f the gas flow has a substantially free unobstructed passage. Preferably adjacent the inlet end of the muffler, a major portion of the gas flow is restricted to increase its velocity while the remainder of the flow is bypassed at a lower velocity. This divided gas flow is collected adjacent the outlet end of the mufller in a common conduit for discharge. Acoustic filters communicate and embrace the straight through conduit and act to vary the sound wave lengths to increasethe wave cancellation. Although the invention is illustrated in connection with a straight through muffler, the principle of the present invention may be applied to modified types of straight through muillers as should be readily appreciated by those skilled in the art.

Referring specifically to the drawing, a muffler lll of the straight through type comprising an outer cylinder shell I2 having headers I4 and I5 at opposite ends define an inlet I8 and an outlet 20, respectively. An intermediate shell 22 is shown supported at opposite ends by the heads I 4 and I6 and intermediate its ends by the annular partition 24 which is preferably perforated as at 26. The shell 22 as disclosed is of uniform diameter throughout its length; however, such construction may not be always desired or found to be necessary. Supported within the shell 22 is a straight through conduit 28 which in the preferred form of the invention consists in a section 30 of less cross-section area than the inlet I8 or the exhaust pipe leading to the inlet I8, a section 32 of substantially the diameter of the outlet 2U and the tail pipe of the exhaust system, and a tapered or restricting connector 36 which communicates the end 34 of the section 30 with the inlet I8. Perforations 38 are provided throughout the length of the conduit 28 including the connector 36 which preferably take the form of elongated slots angularly disposed to the direction of gas flow. The advantages of these perforations over those conventionally employed in mufller constructions is fully discussed in my Patent No. 2,088,296, issued July 27, 1937.

As illustrated, the section 3D of the central tube 28 is of uniform diameter throughout its length, namely, from its point of communication with the connector 36 to its point of communication with the section 32 of enlarged diameter. However, as will be readily appreciated, the connector 36 may be eliminated and the section 30 extended to the inlet I8 and made conical or tapered throughout its entire length or for only a part thereof. Also step-down and step-up tube construction between the inlet I8 and the section 32 or outlet 20 are fully anticipated and fall within the scope of the present invention. With such an arrangement, the central tube 28 might be made up of more than two sections of different diameter.

Partition 39 supports the sections 30 and 32 and defines acoustic lter or resonator chambers 4l), 42, 44, 46, 48 and 5U spaced longitudinally of the muffler. Suitable perforations 52 are provided in the'walls of the tube 22 which constitute the outer Walls of the chambers just men.- tioned. As shown, the perforations 52 take the form of angularly disposed elongated slots. In the preferred form of the invention, the perforated area in the acoustic filter chambers are varied from one end of the muier tothe other. For example, ten slots are provided in each of chambers 4D, 42 and 44, six, four and three slots in chambers 46, 48 and 56, respectively. Because of the differences in cross-section arearbetween .the connector 36 and the sections 30 and 32, the

volumeV of the4 chamber: 41'!y will be less than that of thechambers 42vandf 44: and thevolumeof the chambers 46, 48 and 5D will be the leastY of all the chamber; This difference in volumebetween the chamber acts to varythe length of sound Waves which allows some chance for the sound'waves in the mufflern tocancel each other;

The diameter of the section 30T mayy be varied to: change the frequency or tone of the muiiler Without seriouslyeecting the back pressure measured at the, engine manifold; Changes in the diameter of the; section 310 for such purposes: maybe readilymade in productiony as it is only necessary tol change to partitions 39', connectors Y 36, and connector partitions 52 havingA corresponding inner diameters. ThisV is;V of; particular advantage as different modek vehicles and changes' in engineand/or body design; may require mufers of diierent frequency tone; tov obviate noise periods Another possible.- way of varyingi the frequency or tune of they muiiler` construction herein disclosed resides in the addition or substitution of circular holes or the like in the section 30,. ad-

, jacent the conical connector 36.' Asfully treated inI my aforesaid application, angularlydisposed slotsy in' the straight through' tube give. a much lower frequency note and makes-itv possible to use smaller diameter tubes at the front end of the mii-flier, as the section 36; than could possibly beusedy with conventionalY circular or louver type perforations; By adding, circular holes which may actually cause a whistling by themselves, the muier note as a whole is raised' a few octaves higher which would be suicient, for example, to

place the muiiler frequency or note out. of' phase. with a similar note from some other source of the vehicle. It is to be understood that the high frequency of the whistle created: by the circula-r holes is reduced by the filtering chambers and the onlyeifect is to slightlyv raise the muiiier frequencyv or note. Y

In operation of the embodiment. of the invention illustrated, pulsating exhaust gases from the engine'enter the inlet I8.- As. the connector 36 is tapered or restricted at the inner end, there is a tendency for a portion of the gas ow to be accelerated through theV restricted section 30. The slots in the connector 36 permit a portion of thegasv flow to pass intol the: chamber 40, hence into the outer chamber 5'4; through the aperture- 2,6 into-the outer chamberV 56, and hence intothe section 32- by passing through the chambers 46, 48 and 5U. It isalso possibley for some ofthe gas flow through theV perforations of they connector 36 to be drawn back into the main flow through the section 30 from the chamber 40 or from the chamber 54 through the chambers 42 and 44. It will be appreciated that the gas circuits resulting from the flow through the perforations of the connector 36 into the chamber 54 will have a lower velocity than the flow through the restricted section 30; In practice it has been found' that at low engine speeds the velocity of the exhaust gases is not sufficient to bring acoustic filters of the general type herein disclosed into ecient operation. By accelerating at least a portion of the gas ow in the manner just describedthe mufliing eicient at low engine speeds is materially increased. Also the differential velocity ofthe .gas circuits or streams in the mufer results in increased sound wave cancellation or each, gas stream has its own frequency. Possible objectionable increase in back pressure measured at the engine manifold that might result fromA the restricting action ofthe connector 36. and sectionl iisayoi'ded by the perforation 38 which permits a radial; flow of gas. throughouti the lengthof botlr the connector 3.6 and the section 30. That portion of the gas ow bypassed into the chamber 54, through the perforationI 2:6, andiv into the chamber 56,passes through the chambers 46,V 4.8 and 50, to be collectedv in the section-r 32 and discharged through the outlet 2li. 'Ihe section 32 constitutes a collecting chamber for the straight through and by-passed' gas streams and its cross-sectional areav in most cases will at least approximate orbe greater than that of theV outlet 2U. Also,4 a. collecting chamber in.- addition to the section 32or its equivalentmay be usectv within the scope ofthe invention.

The essence ofthe present invention is` considered to residesinv a` mufer structure generally of the straight through type in. which by restriction, by-passage, and acoustic filtering ofthe exhaust gases, increased sound. waveY cancellation results, pulsations aref reduced: to a steady oW, and objectional back-pressure isV not created. Obviously, the muiii'erstructure for carrying out the principles herein enumerated may be Varied'` materially within the scope of the invention. In

view of this fact it is not desired to limit the in-` vention to the specic structureshown butto include as a part of the invention alli changes in form and: construction as will readily occurto encetoI the area of said inlet, a section of saidcondui-t approximating the diameter of said inlet at one endz and the diameter of said reduced area at the other functioning to-` conduct themajor portion of gas flow from said inlet intoI the reduced section of said conduit, and openings definedin said; last conduit section for bypassing a portion of the gas flow.

2. In a muflier for the exhaust. gases of an internal combustion engine, an inlet, a Ystraight conduit section of uniform diameter for con-4 ducting the major portion ofthe gas flow through the muiiier, said conduit being of less cross-sectional area than said inlet,. a. section of said con duit approximating the diameter of said inlet at one end and the diameter of said reduced area at the other functioning to conduct the major portion of gas flow from said inlet into the reduced section of said conduit, and openings dened in said last conduit section for by-passing a portion of the gas flow.

3. In a muffler for the exhaust gases of an internal combustion engine, an inlet, a straight conduit section of uniform diameter in substantial alignment with said inlet for conducting the major portion of the gas i'low through the mufiler, said conduit being of less cross-sectional area than said inlet, a tapered connector communicating said inlet and said conduit, and openings defined in said connector for by-passing a portion of the gas.

4. In a muiiler for the exhaust gases of an internal combustion engine, an outer shell having an inlet and an outlet, a straight through passageway communicating said inlet and outlet, said passageway including a tapered section, a section of reduced cross-sectional area with reference to said inlet, and a second section approximating in cross-sectional area that of said outlet, said tapered section communicating said inlet and one end of said reduced section, said second section communicating the other end of said reduced section and said outlet, means forward of said reduced section for by-passing a portion of the gas flow around said reduced section to said outlet, and acoustic lter chambers embracing and communicating with said passageway.

5. In a muiiier for the exhaust gases of an internal combustion engine, an outer shell having an inlet and outlet, a straight through passageway communicating said inlet and outlet, said passageway including a tapered section, a section of reduced cross-sectional area with reference to said inlet, and a second section approximating in cross-sectional area that of said outlet, said tapered section communicating said inlet and one end of said reduced section, said second section communicating the other end of said reduced section and said outlet, means forward of said reduced section for by-passing a portion of the gas flow around said reduced section to said outlet, acoustic filter chambers embracing and communicating with said passage- Way, said chambers having diierent volume.

6. In a muffler for the exhaust gases of an internal combustion engine, an outer shell having an inlet and an outlet, a straight through passageway communicating said inlet and outlet, said passageway including a tapered section, a section of reduced cross-sectional area with reierence to said inlet, and a second section approximating in cross-sectional area that of said outlet, said tapered section communicating said inlet and one end of said reduced section, said second section communicating the other end of said reduced section and said outlet, means forward of said reduced section for lay-passing a portion of the gas ilow around said reduced section to said outlet, acoustic lter chambers embracing and communicating with said passageway, and perforations communicating said chambers with the interior of said shell outside of said chambers.

7. In a muiiier for the exhaust gases of an internal combustion engine, an outer shell having an inlet and an outlet, a straight through passageway communicating said inlet and outlet, said passageway including a tapered section, a

section of reduced cross-sectional area with reference to said inlet, and a second section ap-v proximating in cross-sectional area that of said outlet, said tapered section communicating said inlet and one end of said reduced section, said second section communicating the other end of said reduced section and said outlet, means forward of said reduced section for by-passing a portion of the gas ow around said reduced section to said outlet, acoustic lilter chambers embracing and communicating with said passageway, perforations communicating said chambers with the interior of said shell outside of said chambers, the perforated area of said chambers being greatest adjacent the inlet end and being reduced toward the outlet end of the muiller.

8. In a muiiier for the exhaust gases of an internal combustion engine, an outer shell having an inlet and an outlet, a central straight through conduit communicating said inlet and outlet, said central conduit being perforated throughout substantially its entire length and including a reduced section adjacent the inlet and of less crosssectional area than said inlet and an enlarged section adjacent the outlet end of a cross-sectional area at least approximating that of the outlet, and a tapered section between said inlet and said reduced section, an intermediate shell, means dividing said shell into a plurality of acoustic filter chambers embracing said central conduit and spaced longitudinally of the outer shell, perforations in said intermediate shell to enable gases to be by-passed from said central conduit longitudinally of said outer shell through a chamber dened by said outer and intermediate shells, the restricting action of said tapered and reduced sections accelerating a portion of the gas ilow through the central conduit and by-passing a portion of the gas ilow out into said last chamber.

9. In a muiiier for the exhaust gases of an internal combustion engine, an outer elongated shell having an inlet and an outlet at opposite ends, an intermediate shell spaced from said outer shell to dene a longitudinally extending chamber, a central straight through conduit supported Within said intermediate shell in spaced relation, parts spaced longitudinally of said central conduit di- Viding the space between said central conduit and intermediate shell into a plurality of acoustic lter chambers, perforations in said central conduit and intermediate shell communicating the interior of said central conduit with said first chamber through said acoustic filter chambers, said central conduit being proportioned adjacent the inlet end to accelerate a major portion of the gas flow through said central conduit, a portion of the gas flow being by-passed through said perforations to and from said iirst chamber.

l0. In a muiiier for the exhaust gases of an internal combustion engine, an inlet, a conduit of less cross-sectional area than'said inlet communicating with said inlet and constituting a straight through passageway for a major portion of the gas flow through at least a substantial portion of the length of the muler, the portion of said conduit adjacent said inlet end being tapered to accelerate a portion of the gas ilow through said conduit, and perforations in said tapered portion to by-pass a portion of the gas ilow to obviate the creation of objectionable back pressure.

11. In a muler for the exhaust gases of an internal combustion engine of the straight through type, an outer shell having an inlet and an outlet, a straight through central conduit communicating said. inlet andv outlet, acoustic filter chambers embracing said central conduit and communicating with and spaced longitudinal-ly thereof, said central conduit being proportionedi to accelerate a portion` of the gas flow passing therethrough to: increase the efficiency of said acoustic filter chambers at low engine speed, and means for by-passing a portion of the gas flowV adjacent the inlet end to obviate the creation. of objectionable back pressure.

12. In a muier of. theV straight through type, an outer shell having an inlet and an outlet, a centralv straight through conduit communicating endto direct a portion of the gas flow throught" said central conduit at an increased Velocity and to by-pass to said outlet another portion of the gas flow at a lower velocity, the` diierential Velocity of the gas flows and the differential volume, 10

of said acoustic filter chambers acting to increase, the sound Wave cancellation eiect of the muler;

GEORGE A. KINGSLEY.v 

